The present invention relates to a bow dock for use in a two-step docking method to allow the repair or replacement of a sonar dome rubber window on full-draft vessels, or to allow other repair work on the bow portion of these vessels.
A bow dock, or partial floating dry dock, is used to provide a water-free work space around the underwater bow and attendant hull area of a full-draft waterborne vessel. Providing such a work space eliminates the necessity, expense, and time of dry docking the entire vessel to perform routine maintenance on the vessel's sonar dome, or to perform other routine or emergency work on the bow portion of the vessel.
The operation of the bow dock parallels the operation of a conventional floating dry dock except that the physical interaction between the bow dock and vessel is different. A conventional floating dry dock must have a lifting capacity greater than the weight of the vessel so that the dry dock can lift the vessel out of the water. The bow dock does not lift the vessel but instead surrounds the bow and mates with the vessel thus creating a dry and structurally safe work place at the bow of the vessel. The bow dock transmits to the vessel a force sufficient to seal the bow dock with the vessel.
Prior-art bow docks include cofferdam type docks, such as that shown by Howes, U.S. Pat. No. 326,985, or Koulichkov, U.S. Pat. No. 2,360,690, wherein the vessel is positioned in the cofferdam and a seal is created between the hull and cofferdam by means of pivoting or telescoping arms covered with a waterproof shield or apron. The vessel is supported in the cofferdam by keel blocks positioned under the vessel. Other bow docks have been proposed wherein the seal is formed between the dock and the vessel by means of an inflated bladder configured to the hull shape of the vessel. One disadvantage of these docks is that a safe, watertight seal cannot be attained between the dock and the vessel, especially where the dock is to be adapted to numerous classes of vessels.
Another prior-art bow dock, disclosed by King, U.S. Pat. No. 3,326,162, is designed to be used in a one step method of docking a vessel under construction so as to allow the sonar dome to be attached to the vessel. This type dock forms the seal between the dock and the vessel by pivoting a stern gate from the horizontal to the vertical and mating with the hull configuration. The disadvantage of this type dock in draft constrained water is that it can be used only on vessels with a light draft-that can be docked by a one step method of warping the vessel and dock together and then raising the stern gate. On vessels that are fully operational and consequently have a deeper draft, this type of dock and method cannot be used because when the vessel and dock are moved completely together the stern gate of the dock cannot be pivoted to mate with the hull due to the increasing size of the hull. When the vessel is riding deeper in the water, more of the flared portion of the hull is in the water. For the stern gate to form a seal, it must pivot up and forward with respect to the hull and pass by a portion of the hull which is wider than the opening in the stern gate before it reaches the narrower portion of the hull where it is to affect the seal. Because the stern gate opening is smaller than the mid-portion of the hull, the stern gate cannot pivot past the wide portion of the hull to seal with the narrow portion of the hull and thus this type of dock cannot be used with full draft vessels in limited depths of water.